Hydraulic expansion devices for expanding tubes are known in the prior art. In particular, such devices are used to effect an interference-type joint between a reinforcing sleeve and the tube of a heat exchanger, such as a nuclear steam generator. In such steam generators, sludge consisting of boron salts and other corrosive chemicals frequently accumulates in the annular spaces between the heat exchanger tubes and the tube sheet which surrounds them. Over a period of time, these corrosive chemicals, in combination with the hot water which flows around such tubes, can cause corrosion degradation in the outside walls of the tubes in the regions near the tube sheet. If unchecked, such corrosion can ultimately result in fissures in the walls of the tubes, which can cause water leakage through the walls of the tubes. In addition to reducing the efficiency of the steam generator as a whole, such leakage can cause radioactive water from the primary water system to contaminate the non-radioactive water in the secondary water system in the steam generator.
In order to repair these tubes in the tube sheet regions where such corrosion degradation occurs, vaious techniques have been developed for joining reinforcing sleeves on the inner walls of these tubes across the corrosion-degraded portions. This process is called "sleeving". In the prior art, such sleeving was accomplished by means of a three-step process which utilized three distinct tools. In the first step of the process, after the reinforcement sleeve was concentrically disposed within the tube across its corrosion-degraded portion, the ends of the sleeve were hydraulically expanded by the mandrel of a hydraulic expansion unit until they forcefully engaged and plastically deformed the inner walls of the tube. Second, the hydraulically expanded regions were mechanically rolled with a rolling tool in order to strengthen and deepen the interference-type joint between the sleeve and the tube which the hydraulic expansion began. Third, the resulting strengthened joints were brazed with a special electrical-resistance brazing tool to render these joints leakproof.
While such sleeving processes and devices are capable of creating satisfactory interference-type joints between the ends of a reinforcing sleeve and a section of corrosion-degraded tubing, the use of such processes and specialized tools is time-consuming and expensive. In some cases, the three-step procedure makes it difficult, if not impossible, for a maintenance team to perform all of the sleeving repairs necessary in a particular steam generator during the normally-scheduled maintenance "down" times of a nuclear power plant, in which the entire plant is overhauled. This limitation sometimes necessitates setting aside special "down" times for the sleeving operation alone, which can effectively add millions of dollars to the cost of running the nuclear plant. The relative slowness with which such sleeving repairs are made results in high labor costs and the additional negative consequence of exposing the workers on such maintenance teams to a considerable amount of radioactivity. Even though the workers wear protective clothing, the exposure to such radioactivity over such long lengths of time increases the probability of the occurrence of a radiation-related injury. Finally, the use of a separate hydraulic expansion unit, followed by the separate use of a mechanical roller, sometimes makes it difficult to generate a substantially stress-free joint wherein the longitudinal contraction of the sleeve caused by the hydraulic expansion is exactly cancelled out by the elongation of the tube caused by the rolling operation.
Clearly, a need exists for a sleeving apparatus and process which is faster and which obviates the need for exposing maintenance personnel to an inordinate amount of radioactivity. Ideally, such a process and device would also be capable of consistenly providing stress-free joints.